<?php

$array = array("192.168.1.1", "192.168.2.1","192.168.3.1","192.168.4.1","192.168.2.1","192.168.2.1","192.168.10.1","192.168.2.1","192.168.11.1") ;

$cnt_array = array_count_values($array);

echo "<pre>"; 
print_r($cnt_array);

$res = array();
foreach($cnt_array as $key=>$val){
   if($val == 1){
      $res[$key] = 'unique';
   }
   else{
      $res[$key] = 'duplicate';
   }
}

echo "<pre>";
print_r($res);

?>